[Spring] 어노테이션(@)

어노테이션(@)

• @Configuration 어노테이션이 있는 클래스를 ioc 컨테이너가 읽어들이게 되면 해당 클래스 객체를 생성한 후 @Bean 어노테이션이 존재하는 각각의 메소드를 호출하여 bean을 생성 및 관리한다
• 메소드 이름이 xml bean의 id이다

 
 

@Configuration, @Bean

package diEx03;

public class A {
	private String name;
	private String age;
	public String getName() { return name;	}
	public String getAge()  { return age;	}

	public void setName(String name) { this.name = name; }
	public void setAge(String age)   { this.age = age;	 }
}

 
 

package diEx03;

public class B {
	private A a;
	
	public B(A a) {
		this.a = a;
	}

	public A getA() { return a;	}

	public void setA(A a) {	this.a = a;	}
}

 
 

package diEx03;

import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
/*
@Configuration 어노테이션이 있는 클래스를 ioc 컨테이너가
읽어들이게 되면 해당 클래스 객체를 생성한 후 @Bean 어노테이션이 존재하는 
각각의 메소드를 호출하여 bean을 생성 및 관리한다
*/
@Configuration
public class Applicationcontext {
	/* 메소드 이름이 xml bean의 id */
	@Bean
	public A a() {
		A obj = new A();
		obj.setName("홍길동");
		obj.setAge("20");
		return obj;
	}
	
	@Bean
	public B objB() {
		B b = new B(a()); //생성자 주입
		return b;
	}
	
	public A a2() {
		A obj = new A();
		obj.setName("고길동");
		obj.setAge("30");
		return obj;
	}
}

 
 

package diEx03;

import org.springframework.context.annotation.AnnotationConfigApplicationContext;

public class Main {

	public static void main(String[] args) {
		AnnotationConfigApplicationContext ctx 
			= new AnnotationConfigApplicationContext(Applicationcontext.class);
		
		A a = ctx.getBean("a",A.class);
		
		System.out.println("name:"+a.getName());
		System.out.println("age:"+a.getAge());
		
		System.out.println("--------------");
		
		B b = ctx.getBean("objB",B.class);
		System.out.println("name:"+b.getA().getName());
		System.out.println("age:"+b.getA().getAge());
	}

}

 

---

@Component

• ioc 컨테이너가 @Component 어노테이션이 있는 클래스를 읽어 객체로 생성하여 관리한다.  
• 이때 생성되는 클래스 객체의 이름은 클래스 명 첫글자 소문자가 된다
• 주로 해당 클래스로 생성되는 객체가 여러개 일 필요없이 하나만 필요하며 내부 필드가 별도로 없는 경우 사용한다
• 또는 ioc 컨테이너가 생성한 객체만을 필드로 두는 경우

 
 

package diEx04;

import org.springframework.stereotype.Component;

@Component
public class A {
	
	public void method01() {
		System.out.println("A 클래스의 method01 호출!");
	}
	
}

 
 
applicationcontext.xml 에서 Namespaces -> context 체크

 

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
	xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
	xmlns:context="http://www.springframework.org/schema/context"
	xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd
		http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context-3.2.xsd">
	
	<!-- 해당 패키지 안 클래스들 중 @Component 어노테이션이 있는 클래스의 bean 생성 -->
	<context:component-scan base-package="diEx04" />
</beans>

 
 

package diEx04;

import org.springframework.context.support.AbstractApplicationContext;
import org.springframework.context.support.GenericXmlApplicationContext;

public class Main {

	public static void main(String[] args) {
		AbstractApplicationContext ctx = 
				new GenericXmlApplicationContext("classpath:applicationcontext.xml");
		
		A a = ctx.getBean("a",A.class);
		
		a.method01();
	}

}

 
 
 

package diEx04;

import org.springframework.stereotype.Component;

@Component(value="objB")
public class B {
	
	public void method01() {
		System.out.println("B 클래스의 method01 호출!");
	}
}

 

package diEx04;

import org.springframework.context.support.AbstractApplicationContext;
import org.springframework.context.support.GenericXmlApplicationContext;

public class Main {

	public static void main(String[] args) {
		AbstractApplicationContext ctx = 
				new GenericXmlApplicationContext("classpath:applicationcontext.xml");
		
		A a = ctx.getBean("a",A.class);
		a.method01();
		System.out.println("------------");
		
		B objB = ctx.getBean("objB",B.class);
		objB.method01();
		System.out.println("------------");
		
	}

}

 
 
 

어노테이션 기반 의존 주입

package diEx04;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Component;

@Component
public class C {

	private A a;
	
	/* 생성자 의존 주입. 타입이 일치하는 1개를 넣어준다 */
	@Autowired
	public C(A a) {
		this.a = a;
	}
	
	public void method01() {
		System.out.println("C 클래스 호출 method01!");
		a.method01();
	}
}

 
 

package diEx04;

import org.springframework.context.support.AbstractApplicationContext;
import org.springframework.context.support.GenericXmlApplicationContext;

public class Main {

	public static void main(String[] args) {
		AbstractApplicationContext ctx = 
				new GenericXmlApplicationContext("classpath:applicationcontext.xml");
		
			
		C c = ctx.getBean("c",C.class);
		c.method01();
		
		
	}

}

 
 
 
@Autowired 어노테이션은 타입을 기준으로 생성되는 bean(객체)의 의존성을 주입할 수 있다
이때 타입이 같은 bean을 ioc에서 여러개 가지고 있다면 두번째로 이름이 같은 bean을 주입한다
1번째로 타입확인 : B 타입은 b, objB 두개
2번째로 이름확인 : b
 
@Qualifier("객체이름") 어노테이션을 사용하면 특정 bean의 이름을 지정할 수 있으나
생성자에서는 사용할 수 없다

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
	xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
	xmlns:context="http://www.springframework.org/schema/context"
	xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd
		http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context-3.2.xsd">
	
	<bean id="b" class="diEx04.B" />
	
	<!-- 해당 패키지 안 클래스들 중 @Component 어노테이션이 있는 클래스의 bean 생성 -->
	<context:component-scan base-package="diEx04" />
</beans>

 
 

package diEx04;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Component;

@Component
public class D {
	
	private B b;
	
	
	@Autowired
	public D(B b) {
		this.b = b;
	}
	/*
	bb 가 없어서 오류발생
	public D(B bb) {
		this.b = bb;
	}
	*/
	
	
	public void method01() {
		System.out.println("============================");
		System.out.println("D 클래스에서 method01() 호출");
		b.method01();
		System.out.println("============================");
	}
}

 
 

package diEx04;

import org.springframework.context.support.AbstractApplicationContext;
import org.springframework.context.support.GenericXmlApplicationContext;

public class Main {

	public static void main(String[] args) {
		AbstractApplicationContext ctx = 
				new GenericXmlApplicationContext("classpath:applicationcontext.xml");
		
		A a = ctx.getBean("a",A.class);
		a.method01();
		System.out.println("------------");
		
		B objB = ctx.getBean("objB",B.class);
		objB.method01();
		System.out.println("------------");
		
		B b = ctx.getBean("b",B.class);
		b.method01();
		System.out.println("------------");
		
		C c = ctx.getBean("c",C.class);
		c.method01();
		
		D d = ctx.getBean("d",D.class);
		d.method01();
	}

}

 
 
 

package diEx04;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.beans.factory.annotation.Qualifier;
import org.springframework.stereotype.Component;

@Component
public class E {
	
	@Autowired
	private A a;
	
	private B bb;
	
	@Qualifier("objB")
	@Autowired
	public void setB(B bb) { this.bb = bb; }
	
	public void method01() {
		System.out.println("--------------------------");
		System.out.println("E 클래스 method01() 호출!");
		a.method01();
		bb.method01();
		System.out.println("--------------------------");
	}
}

 

package diEx04;

import org.springframework.context.support.AbstractApplicationContext;
import org.springframework.context.support.GenericXmlApplicationContext;

public class Main {

	public static void main(String[] args) {
		AbstractApplicationContext ctx = 
				new GenericXmlApplicationContext("classpath:applicationcontext.xml");
		
		A a = ctx.getBean("a",A.class);
		a.method01();
		System.out.println("------------");
		
		B objB = ctx.getBean("objB",B.class);
		objB.method01();
		System.out.println("------------");
		
		B b = ctx.getBean("b",B.class);
		b.method01();
		System.out.println("------------");
		
		C c = ctx.getBean("c",C.class);
		c.method01();
		
		D d = ctx.getBean("d",D.class);
		d.method01();
		
		E e = ctx.getBean("e",E.class);
		e.method01();
	}

}